When it comes to lighting, both indoors and out, it can feel like there are dozens of options available. String lights, spot lights, flood lights, the list goes on and on. However, these are all just form factors that can shape and disperse light in different ways. There are really only two lighting technologies that can create colored light effects – incandescent and LED. Understanding their differences, strengths, and weaknesses will help you make the best choice for each and every scene.
Basis of Operation
Incandescent light as we know it today is one of the first electric light technologies to be invented and commercialized. The principle of operation is very simple – heat up a wire until it glows. This wire, called the filament, has been optimized to release the most light for a long period of time before breaking down, but quite a bit of heat is still generated alongside the light. While commercial bulbs are optimized to operate with the voltage that comes out of the wall, any amount of power will eventually cause the filament to heat up and glow.
LEDs (light emitting diodes) operate very differently. While an entire incandescent bulb is considered one light-producing unit, LEDs are much smaller, passive electrical components that can be as large as your thumbnail or as small as a grain of rice. When you buy an incandescent-replacement bulb, it is actually several LED light sources clustered together to fit the same form factor as a traditional bulb. LEDs produce more light than heat, but require a low DC voltage and cannot be run directly from wall power. LEDs are also much more robust than incandescent bulbs. They do not have a glass bulb that can be broken into dangerous shards, and generate light using solid state electronics rather than a fragile strand of filament.
While some incandescent bulbs will glow with a warmer (more orange) or cooler (more blue) tint, they all produce white light. They only way to get a colored light is to pass this white light through a colored lens. The bad news is that a colored dome or film blocks some of the light, further reducing the efficiency. Since incandescent bulbs are only around 10% efficient anyway (a 100W bulbs is actually generating 10W of light and 90W of heat), this heat can be dangerous in enclosed spaces. On the flip side, we are very good at producing a wide range of colored plastics, so if you are using a spot or projection light colored with sheets of film, you can theoretically get just about any color you want. Commercial offerings are typically not very creative, and you will usually not find anything beyond very standard primary and secondary colors at a big box store.
Image from OogaLights.com
LEDs come in a wide range of colors that are generated by the properties of different materials used to make LEDs; instead of passing white light through a film. So you can easily get LEDs that are red, green, blue, etc. without any drop in efficiency. You can, of course, still pass white LED light through a colored film, but the more popular color mixing method is to use natively red, green, and blue LEDs very close together and controlling the relative brightness of each color. These multi-color LEDs are often found in the same light emitting unit, often labeled as an “RGB LED”. RGB always means red, green, blue, since those are the three primary colors of light that can be combined to make any color of light. Some of these combo LEDs also include a dedicated amber (RGBA), white (RGBW), or warm white (RGBWW) component to make it easier to generate warmer colors. Even though white is technically a blend of red, green, and blue and the little LEDs are very close together, our eyes can usually distinguish which side of a “white” light has more green or red, so an RGBW LED lets you generate a perfect white.
Close-up of RGB LED from core-electronics.au
Controlling and Powering the Lights
Incandescent bulbs cannot dynamically change color, so control is limited to brightness. Incandescent bulbs can be used with any standard dimmer, and are thus easy to control manually. Because they require high AC voltages (like 120VAC in the US) to operate as expected, the circuitry required to automate any sort of dimming or on/off control tends to be bulky and expensive.
LEDs on their own require a voltage of 2-5 VDC, depending on the color. Commercial products will typically group LEDs together such that they can operate off a higher voltage, like 12VDC or 24VDC, but do not work with AC power that comes out of the walls. Wall power must be changed into a low DC voltage, usually through a converter colloquially called a “power brick”. Because LEDs use a much lower DC voltage, they are easier to control and many hobbyist-oriented boards like the Arduino or RaspberryPi have extensive example scripts to help you get started. These projects let you control both the brightness of the LEDs and the color of RGB LEDs. If you have a strip of individually addressable LEDs you will be able to control the color of each light source individually, but most LED strips require you to change all the LEDs’ colors at once.
Image from dhgate.com
So, What to Use?
While LEDs have gotten significantly cheaper over the last decade, their dynamic colors and high efficiency still make them more expensive than their incandescent counterparts. Use LEDs anywhere that you want to control the lights and/or where heat can be an issue (such as in an indoor scene), but incandescent lights are typically fine for outdoor decoration or low-level ambient lighting as long as they are not at risk of getting broken. In fact, the heat generated by an incandescent light can help melt off any early-season snow! Knowing where you can tolerate a little heat vs. need efficiency and precise color control will make picking lights easier this season, no matter which form factor you need.